Sidemount vs Backmount Doubles: Which to Learn First

Learn the one that fits your goals. Backmount doubles suit most open-water technical diving and a team in the same rig. Sidemount suits restrictive spaces, carrying cylinders separately and some backs. UTD lets you take its open-circuit courses in either, and its Z-System sidemount keeps the same long-hose donation and necklace backup.

By Jeremiah Gardner · Last reviewed October 27, 2026

Once you're ready for doubles, the next question is which kind: two cylinders on your back, joined by a manifold, or two cylinders at your sides. Both are valid. The right answer depends on what you want to do with them.

The quick comparison

	Backmount doubles	Sidemount
Where the cylinders sit	On your back, joined by an isolator manifold	Under your arms, clipped to your harness
Best for	Open-water technical diving, wrecks, team dives in a common rig	Restrictive spaces, carrying cylinders separately, some backs and bodies
Getting in and out	Heavy on land; put on before entry	Cylinders can be carried one at a time and clipped on in the water
Valve access	Behind your head	In front of you
Gas management	One manifolded supply with an isolator	Two cylinders, managed independently or through a manifold such as UTD's Z-System
Team consistency	Classic DIR configuration	Consistent with backmount when set up for long-hose donation

When does backmount make sense?

If your goal is open-water technical diving, like deeper reefs, wrecks and decompression, backmount doubles are the classic choice. The gas supply is joined by a manifold, so both cylinders drain together. The isolator lets you separate them if a problem develops. Most technical teams use the same rig, so procedures and gas sharing are identical across the team.

When does sidemount make sense?

Sidemount shines in a few situations:

Restrictions. A diver with cylinders at their sides is slimmer from above, which matters in caves and tight wrecks.
Carrying cylinders. You carry one cylinder at a time and clip them on in the water, which helps on shore entries and for divers who can't carry heavy doubles.
Some backs and bodies. Some divers find sidemount more comfortable on land and in the water.

Does sidemount change gas sharing?

Not in UTD's system. UTD requires any sidemount rig used in its courses to allow the same long-hose and necklace donation as backmount, so the S-drill works the same way.

What changes is behind the regulators. UTD's Z-System feeds both regulators through a distribution block, so a backmount diver and a Z-System diver donate the same way, but the failures and how you isolate them are different. UTD's sidemount training covers those failures. And your team needs to know the differences before the dive.

What about independent sidemount?

Many sidemount divers use two independent regulators, one on each cylinder, and switch between them during the dive to keep the cylinders balanced. That works, but gas sharing and failure procedures differ from backmount. UTD's sidemount training covers the theory of independent doubles as well as the Z-System. Whichever you dive, your team needs to know how you'll donate gas.

Which should you learn first?

Heading into open-water technical diving with a backmount team? Start with backmount.
Heading toward caves or restrictive wrecks, or carrying heavy cylinders is a problem? Sidemount is worth a serious look.
Not sure yet? Choose the one your local team dives. Diving the same system as your teammates matters more than the system itself.

Either way, don't buy first. Train in a configured rig, then buy what fits.

Learn it properly

Our Doubles (Backmount or Sidemount) course trains the normal and emergency skills of double-cylinder diving in either configuration, including valve drills and gas failures. For how doubles fit into the rest of the configuration, see DIR Gear Configuration, Piece by Piece.

Frequently asked questions

Can I take UTD technical courses in sidemount?

Yes. UTD's open-circuit courses can be taught in backmount or sidemount, single or doubles, unless a course standard says otherwise.

What is the UTD Z-System?

UTD's sidemount system. Both cylinders feed a distribution block, so you donate a long-hose primary and breathe a necklace backup, just like backmount. The plumbing behind it is different, so failures are handled differently. Sidemount training covers them.

Is sidemount easier on your back?

Many divers find it easier to carry cylinders one at a time, and to put them on in the water. That's a real advantage for some bodies and some dive sites.

Do I need to learn both?

No. Many divers dive one configuration for years. If you do learn both, a system that keeps gas sharing and procedures consistent makes switching much easier.